1. Field of the Invention
The present invention relates generally to a lubrication device for an engine, and more specifically to a lubrication device for supplying lubricant to a chain incorporated in a DOHC engine.
2. Description of the Prior Art
To obtain higher engine performance in automotive vehicles, DOHC (double overhead camshaft) engines have been widely used, in which two different camshafts for driving intake and exhaust valves independently are mounted on a cylinder head. In some DOHC engines, an idler sprocket (an intermediate gear) is arranged between a crankshaft and two camshafts; a first chain is reeved around the crankshaft and the idler sprocket; and a second chain is reeved around the idler sprocket and the two camshafts. During engine running, the idler sprocket is driven by the crankshaft via the first chain, and the two camshafts are driven by the idler sprocket via the second chain.
In the above-mentioned DOHC engine, however, since the second chain is located farther frontward away from the front end surface of the cylinder head or the block than the first chain, conventionally a separate oil passage for supplying oil only to the second chain is additionally formed in the cylinder block and further an oil jet pipe member is additionally pressure fitted to a hole formed on the front end surface of the cylinder block near the second chain, in order to jet lubricant to the second chain, as disclosed in NISSAN FJ20 ENGINE MAINTENANCE MANUAL, on pages 5 and 6published by NISSAN Corp. in March, 1982, with a result that a complicated lubrication device is provided for the cylinder block of a DOHC engine.